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A liquid antioxidant composition for raw rubbers

IP.com Disclosure Number: IPCOM000248743D
Publication Date: 2017-Jan-04
Document File: 55 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

This article relates to a liquid antioxidant composition and more specifically, it relates to a liquid antioxidant composition for raw rubber products. Raw rubbers like natural rubbers, styrene-butadiene copolymers, polybutadiene, polyisoprene and so on are obtained from natural resources or solution polymerization of monomers undergoing processes of polymerization, evaporation, granulation and packaging but without vulcanization. Normally, antioxidants are added into rubbers at the end of polymerization to keep rubbers from coloration, gelation and deterioration of physical properties caused by oxidation during these processes as well as in storage. Before added into the raw rubber solution, antioxidants are dissolved in solvent of solution polymerization first to facilitate the even distribution of antioxidants in raw rubber solution. Antioxidants agents often used in raw rubbers are hindered phenol-based agents. Phosphite-based antioxidant agents could be used together with hindered phenol-based antioxidant agents as auxiliary antioxidant to enhance anti-oxidation properties. Aromatic amine-based antioxidants agents have stronger anti-oxidation ability, but they tend to stain the raw rubbers. Limited amount of specific aromatic amine-based antioxidants could eliminate disadvantage of staining. Among various hindered phenol-based, aromatic amine-based antioxidant agents and phosphite-based antioxidant, part of them are in solid at room temperature and therefore not applicable for production operation of raw rubbers. Even for antioxidant liquid at room temperature, there still exists problem, i.e., they tend to freeze at low temperature since their freezing point is normally higher than 15°C, which severly restricts the application in wide temperature range. Patent application CN103435956A disclosed an antioxidant composition for SBS (block copolymer of styrene and butadiene) comprising 1 part of 4-hydroxyl-3, 5-di-tertbutyl C7-C9 mixed alcohol ester of phenpropionate, 1.8 to 2.2 parts of 2-methyl-4, 6-di-(octylsulfanylmethyl)phenol, 0.8 to 1.2 parts of reaction product of N-phenylphenylamine and 2, 4, 4-trimethylpentene. The obtained antioxidant composition is dissolved in cyclohexane first before added into SBS resin solution. And cyclohexane is the solvent of solution polymerization of SBS. The dissolving rate is low because of the polarity discrepancy between cyclohexane and antioxidant composition. Furthermore, cyclohexane has a boiling point of 80.74 °C, which is lower than that of water. In "drying" step of preparing raw rubbers, i.e. removing solvent as well as monomer residue from rubber resins by hot water or steam, antioxidants tend to move into water, which brings a significant decrease of efficient antioxidants in raw rubbers. Moreover, the contaminated water requires further treatment to avoid polluting environment. Therefore, it is still required to provide a new liquid antioxidant composition that is stable during "drying" process of rubber resins synthesized via solution polymerization, non-staining as well as applicable for wide temperature range besides sufficient anti-oxidation.

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A liquid antioxidant composition for raw rubbers

1

This article relates to a liquid antioxidant composition and more specifically, it relates

to a liquid antioxidant composition for raw rubber products.

Raw rubbers like natural rubbers, styrene-butadiene copolymers, polybutadiene,

polyisoprene and so on areobtained from natural resources or solution

polymerization of monomers undergoing processes of polymerization, evaporation,

granulation and packaging but without vulcanization. Normally, antioxidants are

added into rubbers at the end of polymerization to keep rubbers from coloration,

gelation and deterioration of physical properties caused by oxidation during these

processes as well as in storage. Before added into the raw rubber solution,

antioxidants are dissolved in solvent of solution polymerization first to facilitate the

even distribution of antioxidants in raw rubber solution.

Antioxidants agents often used in raw rubbers are hindered phenol-based agents.

Phosphite-based antioxidant agents could be used together with hindered phenol-

based antioxidant agents as auxiliary antioxidant to enhance anti-oxidation

properties. Aromatic amine-based antioxidants agents have stronger anti-oxidation

ability, but they tend to stain the raw rubbers. Limited amount of specific aromatic

amine-based antioxidants could eliminate disadvantage of staining.

Among various hindered phenol-based, aromatic amine-based antioxidant agents

and phosphite-based antioxidant, part of them are in solid at room temperature and

therefore not applicable for production operation of raw rubbers. Even for antioxidant

liquid at room temperature, there still exists problem, i.e., they tend to freeze at low

temperature since their freezing point is normally higher than 15oC, which severly

restricts the application in wide temperature range.

Patent application CN103435956A disclosed an antioxidant composition for SBS

(block copolymer of styrene and butadiene) comprising 1 part of 4-hydroxyl-3, 5-di-

tertbutyl C7-C9 mixed alcohol ester of phenpropionate, 1.8 to 2.2 parts of 2-methyl-4,

6-di-(octylsulfanylmethyl)phenol, 0.8 to 1.2 parts of reaction product of N-

phenylphenylamine and 2, 4, 4-trimethylpentene. The obtained antioxidant

composition is dissolved in cyclohexane first before added into SBS resin solution.

And cyclohexane is the solvent of solution polymerization of SBS. The dissolving rate

is low because of the polarity discrepancy between cyclohexane and antioxidant

composition. Furthermore, cyclohexane has a boiling point of 80.74oC, which is lower

A liquid antioxidant composition for raw rubbers

2

than that of water. In “drying” step of preparing raw rubbers, i.e. removing solvent as

well as monomer residue from rubber resins by hot water or steam, antioxidants tend

to move into water, which brings a significant decrease of efficient antioxidants in raw

rubbers. Moreover, the contaminated water requires further treatment to avoid

polluting environment.

Therefore...